Refrigerated cabinet with circulating air panels



Feb. 8, 1966 s. BECKWITH ETAL 3,233,423

REFRIGERATED CABINET WITH CIRCULATING AIR PANELS Filed Dec. 26, 1962 4eZ 26g Qt )1 20 Z 74 FIG-3.5

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G 2 INVENTORS BY m 3,233,423 Patented Feb. 8, 1966 United States PatentOfifice 3,233,423 REFRIGERATED CABINET WITH CIRCULATING AIR PANELSSterling Beckwith, Lake Forest, and Robert E. Vogel,

Deerfield, Ill., assignors to Dual Jet Refrigeration Company, Chicago,IlL, a corporation of Illinois Filed Dec. 26, 1962, Ser. No. 247,245 6Claims. (Cl. 62-256) This invention relates to an improved refrigerationsystem which is characterized by a unique arrangement for efiicientlymaintaining refrigeration. The invention is particularly directed todevices of the type which are capable of maintaining a refrigeratedstate within an enclosed space while still providing an opening foraccess to the contents.

In an application of Hagen et al., Serial No. 54,077, filed September 6,1960, now Patent No. 3,134,243, granted May 26, 1964 and in the issuedSimons Patent No. 2,862,369, there are'described refrigerated displaycabinets which are provided with access openings exposed to theatmosphere while still being capable of maintaining the contents in arefrigerated state. Loss of refrigeration from the enclosed spacethrough the access opening is reduced in a highly effective manner inthese constructions by the use of a gaseous, preferably air, curtainwhich is continuously advanced across the open side from one edge of theopening to the opposite edge. The air curtain in these constructions isadapted to be formed of adjacent panels of air, with the innermost panelcomprising a refrigerated cold air panel, and with one or more outerpanels having temperatures approaching the ambient temperature. It hasbeen found that it is desirable to recirculate the inner cold air paneland to provide means for circulating the adjacent guard panels, toconserve the refrigeration and to maintain the enclosed space in asatisfactory refrigerated state.

In these constructions there are described assemblies which includenozzles extending across the bottom edge of the access opening to directthe air panels upwardly across the opening towards inlets which extendacross the top side of the access opening. As an alternative, thenozzles are located across the upper edge for projecting the air panelsdownwardly toward inlets arranged aacross the bottom edge. It is alsocontemplated that the air nozzles be located across one of the lateraledges of the opening for directing the corresponding air panels acrossthe opening toward inlets in the opposite edge. Because of the moredesirable effect of gravity on the higher density cold air, it has beenfound preferable to provide the air curtain with a downward movementfrom nozzles across the top to inlets across the bottom. The followingdescription will refer to this preferred construction, although it willbe understood that the con cepts to be described are also applicable toother directions of flow.

In the use of cabinets of the type described, it is, of course,desirable to provide maximum efficiency insofar as the amount of powerconsumed is concerned. In refrigeration systems of this type, theconsumption of power is primarily due to the refrigeration of the movingair streams which pass over the access opening for the cabinet. To asomewhat lesser degree, power is consumed during defrosting cycles anddue to the driving of fans for circulation of the streams. As far as therefrigeration of the streams is concerned, a major factor contributingto the amount of power consumption is the loss of refrigeration (orintake of heat) through the access opening.

It is an object of this invention to provide a refrigerated cabinetconstruction which is provided with means for decreasing the powerconsumption necessary for maintaining a desired level of refrigeration.

It is a more particular object of this invention to provide arefrigerated cabinet which is provided with means for decreasing theloss of refrigeration or intake of heat through the access opening ofthe cabinet.

It is an additional object of this invention to provide a method forcontrolling the characteristics of the air streams passing across theaccess opening whereby loss of refrigeration is avoided and a decreasein power consumption is realized.

These and other objects of this invention will appear hereinafter, andfor purposes of illustration, but not of limitation, specificembodiments of this invention are shown in the accompanying drawings inwhich:

FIGURE 1 is a schematic elevation in section of a refrigerated enclosurecharacterized by the features of this invention; and

FIGURES 2 and 3 illustrate schematically alternative passage and nozzleconstructions characterized by the features'of this invention.

As indicated, the improvements of this invention are directed torefrigerated enclosures of the type which define an access opening inone wall, which is provided for communication with the otherwiseenclosed space. The enclosures are provided with a plurality of nozzlesarranged in side-by-side relationship across one edge of an accessopening, and corresponding inlets are located across an opposite edge ofthe access opening. The inner nozzles and inlets are provided for thepassage of refrigerated streams across the access opening, while theouter nozzles and inlets circulate progressively warmer air panels. Theinner refrigerated streams are circulated through passages havingrefrigeration coils or the like situated therein, and one or more of theouter streams may also be refrigerated. a

In accordance with this invention, it has been found that if means areprovided for controlling circulation of the air panels in a certainmanner, then a greater degree of efficiency, insofar as loss ofrefrigeration is concerned, can be obtained. Specifically, it has beenfound that by providing for control of the speed of circulation of theair streams, whereby the inner streams move at a higher speed thanadjacent outer streams, the desired results can be accomplished.

In one aspect of this invention, one or more of the inner streams of airare powered as by circulating fans located in the cabinet passages. Anouter stream of air is adapted to circulate through an outer passage.However, circulating fans are not provided for powering this stream.This outer stream is adapted to circulate by means of contact with anadjacent powered stream as the air panels formed by the streams passacross the access opening of the cabinet. Since the outer panel iseffectively dragged along through frictional contact with the adjacentpanel of the powered stream, the outer stream will inherently move at aslower average speed.

In a further aspect of this invention, adjacent streams are powered sothat they move at different speeds to accomplish the desired effect.Specifically, this form of the invention provides for a greater speed inthe innermost of two adjacent streams, with progressively decreasingspeeds prevailing in panels formed by outer streams.

Various combinations of powered and non-powered air streams anddifferent cabinet designs having two or more air passages arecontemplated. Thus, a cabinet having a pair of inner powered streamswith an outer stream circulated through contact with an adjacent poweredstream represents one possible combination of the above describedconcepts. On the other hand, cabinets having two passages adapted tocirculate a faster inner passage 34.

stream and an adjacent slower stream can be provided with twocirculating fans or a single fan for the inner stream. Obviously, theprovision of a circulating fan for each passage in a cabinet, includingthree or more passages, also falls-within the scope of this invention.

The accompanying drawing illustrates a refrigerated cabinet which ischaracterized by means for practicing the invention. The cabinetincludes a top wall 12, bottom wall ld, back wall. 16 and afront wall18. The structure defined by thesewalls is located on a support 20. Thefrontwall 18 defines an opening 22 which provides access ro-an enclosedrefrigerated space 24. The inner wall 26 defines the extent of therefrigerated space. A pair of partitions 28 and 30 are locatedintermediate the inner andouter walls and define with these wallspassages -32, 34, and 36.- These passages confine air streams which areadaptedto be circulated through the cabinet. The streams intheembodiment illustrated form laminar panels-38,- 40, and 42 which passacross the access opening. Screens 48 can be provided over inletopenings 46 for -thepassages in order to prevent entry-of insects orothenforeign material.-

Nozzles 44 are provided at theendsof each of the passages, and the airstreams pass through these nozzles toward inlets46 which communicatewith the passages at the opposite end of the access opening. The nozzles44 preferably comprise constructions of the type disclosed in co-pendingapplication Ser; No. 91,875 entitled Refrigerated Display Case andElements Thereof. Such nozzles may comprise aplurality of parallel,longitudinally spaced vanes or members which subdivide the noz zle intoa number of closely separated parallel passages. The nozzles form acontinuation of the passages which confine the streams circulatingthrough the cabinet housing i In the preferred practice ofthe-invention, the nozzle sections are formed of honeycomb which may bemanufactured of sheet aluminum. The vmost satisfactory honeycombsections havea depth greater than /2 inch and preferably greaterthan oneto two inches so that streams of air issuing from the honeycomb will beguides in laminar flow across the access opening in the front wall ofthe cabinet.-

In thecabinet'illustrated,-the inner passage 36 is provided with acirculating-fan 50 and a refrigeration means 52. The air panel formed inthis passage is adapted to be circulated by means of the fan intocontact with the refrigeration means and then passes out. throught-heinnermost nozzle 44-as the refrigerated panel 42. The innermost streamis thus the coldest stream, while the streams and 38- are progressivelywarmer. As above explained, this arrangement permits access through thefront opening of the cabinet while still providing an effectiverefrigerating operation.

A circulating fan 54 is provided for the intermediate In accordance withthe concepts of this invention, the fan 54 is adapted to operate atlower speed so that the panel 40 will move more slowly than the panel42.

There is no circulating means provided in the passage 32 which confinesthe outermost stream of air. However, the outer stream form a panel ,38which contacts panel was these panels crossthe access opening. Thisarrangementcfthe panels causes the panel 38 to be dragged by the panel40 so that the outer panel circulates, although at a lower speed.

. As previously indicated, various alternatives are available insofar asthe arrangement of the panels and design of the panel are concerned.Thus, the outer passage 32 could be eliminated, providing either twopassages each having a circulating fan, or two passages with only thefan 5.4. If three passages are retained, alow capacity circulating fancould be provided for the outer stream.

It is also contemplated that the feature of a nonpowered stream could beemployed in combination with two or more inner streams which operate atthe same speed. Thus, there are advantages in employing the differentialoperation of the outer stream, even if the same speeds prevail in thetwo inner streams. On the other hand, a fast moving innermost streamcould be utilized in combination with twoor more outer streams moving atthe same speed. These alternatives, although providing in someinstancesless advantageous results, have utility, particularly whereequipment for providing complete differentials in the air panels is notavailable.

Although it is notthe. applicants intentionfto limit the invention toany particularly theory, it is believed that the advantageous resultsarise due to an interaction between the respective .movingpanelsas theycross the access opening. Specifically, it is believed that. the facesof moving panels are subject to mixing with. respect to the adjacentstil l air and that the amount o-frnixing determines the amount of heatloss from the panels. It has also been observed that the mixing is afunction of the velocity of the panels, and that, therefore, the amountof heat loss is dependent on thevelocities.

The .mixing or turbulence is believed to result in the heat loss becauseofa whipping actionto setup in the streams. ,Thus, air. turbulenceoccursat the interface between-adjacent streams,and there is then atendency for the streams to be displaced from a direct path acrosstheaccess opening. This displacement,.which occurs most readily near theend of travel of the streams acrosssthe opening, takes the form of backand forth movement, and, it will be appreciated that swbstantialamountsof the. cold .air in thestreams will be displaced toward.the...outside of the cabinet. as a result of this whipping action... .ltwill. also be appreciated that the occurrence of turbulence necessarilyresults intlie mixing of. colderair. with the. adjacent outer airwhereby the colder. air is moved out of the innermost streams. It .hasbeen found that operation of the intermediate stream .40 at a lowerspeed than .the stream 42 can be carried. out .without resulting insignificant turbulence or mixing at the interface 58 between the streams42 and 40. If the. respective speeds are properly regulated, thesestreams slip by one another and, therefore, the laminar character of therespective streams is maintained. 'Ilhemaintenance of this laminarcharacter substantially preserves thetemperature differential betweenthe. inner refrigerated stream and the adjacent guard stream.

It is Well-known that laminar fiow of fluids can be maintained even "though a differential exists in the speed of different portions of thefluid. If the. differential exceeds a certain value, it is alsowell-known that turbulence WilLresult andlaminar flow will not bepossible. Thus, .the relative speeds of the panels must be maintainedwithin the limits which enable substantial laminar flow.

A barrier to the inflow of warm air results at the outer face 60 of thestream 40 in the illustrated cabinet. Thus it has been determined that alaminar character also existsat this interface since the streams 46 and38 can be caused to slip with respect to each other.

The outermost stream 38 will create a minimum of turbulence with theambient air at the face 62 of this stream. This is the case, since theaverage velocity of this stream is low, and since the outermost portionsof this stream will necessarily have 2. below average velocity.Accordingly, the small turbulence created does not cause inflow of warmair to any great extent.

It has been observed that higher temperatures are recorded in the lowerpart of cabinets when a pair of streams comprising a refrigerated streamand a guard stream are moved at the same speed across the accessopening. The use of a third stream whether or not it is powered, did nottotally avoid this situation. How ever, when the speed of the innerstream was increased,

this detrimental condition was effectively avoided and substantiallyuniform temperature conditions were recorded. The improved operation wasattributed to a reduction in whipping caused by the greater throwcreated by the higher velocity of the inner stream. With the whippingreduced, laminar flow was maintained for a longer distance and areduction in heat loss realized. To illustrate, if the inner air panelis at 25 F. when at the top of the cabinet, the further it travelswithout significant mixing with the adjacent stream, the lower thetemperature will be at the intake nozzle. If a temperature of about l5F. is preserved at this point, then the burden on the refrigeratingcoils is not extreme. Furthermore, a maximum temperature of F. withinthe enclosure is assured.

In a typical operation, the speed of the inner refrigerated stream ismaintained at about 400 ft. per minute, while the adjacent guard panelis moved at about 275 ft. per minute. Where an outer panel is employed,it is pulled along at an average speed between 50 and 75 ft. per minute.As previously suggested however, the relative speeds are determined witha view toward maintaining laminar flow and eliminating turbulence. Itwill be understood that many combinations of speed are available foruse.

It will be appreciated that the various speed values can be changed tosuit different conditions such as the desired temperature within thecabinet, the prevailing ambient temperature and similar conditions. Ithas been found that speeds in the inner panel in excess of 300 ft. perminute provide the results of this invention, while the adjacent guardpanel can be maintained at speeds between 200 and 300 ft. per minute.The true limiting factor on the values, however, is related to theeffect of the speeds on the turbulence in the various planes made up bythe faces and interfaces of the streams. Thus, the speed of the adjacentguard panel is maintained at a sufficiently high level to provideslippage between these laminar streams thereby avoiding turbulence atthe interface of these streams. If an outer panel is employed, the speedis preferably maintained below about 100 ft. per minute, or at a levelwhich minimizes creation of turbulence between the stationary ambientair and the slow moving guard panel.

It is also contemplated in accordance with this invention to providemeans for producing variable speeds across individual panels in theapparatus. Specifically, the invention is intended to cover the use ofmeans adapted to control the movement of portions of a panel, such asthe panel 40, whereby the innermost portions of the panel move fasterthan adjacent portions, with a progressive decrease in speed to theouter portions.

FIGURES 2 and 3 illustrate two examples of means capable of effectingthis result. It will be appreciated from the following discussion thatvariations in the design of these means will produce substantially thesame results and various other mechanisms for producing these resultswill be obvious to skilled observers.

The structure shown in FIGURE 2 comprises a passage 70 extending to anoutlet opening 72. A honeycomb section 72 is fitted into the outlet inthe manner previously described. A plurality of vanes 76 are positionedto extend across the passage upstream of the outlet and it will be notedthat these vanes are equally spacedapart at their leading edges. Thespacing between the vanes changes toward the trailing edges thereof in amanner such that a progressively increasing spacing toward the outsideof the passage results at the exit ends of the vanes.

When a stream of air is circulating through the passage 70, the vanes 76will divide the streams into equal portions. Since the same amount ofair must pass through openings of a different volume, the speeds of theair will vary in a corresponding manner. By providing the progressivelyincreasing openings toward the outside of the passage 70, the innermoststream will move faster than the adjacent stream and this adjacentstream will move faster than the next stream and so on. When theseportions of the streams pass through the honeycomb section and acrossthe access opening, they will move at different speeds, however, thespeeds are regulated by the design of the vanes so that turbulence willnot be set up by the adjacent portions of the stream. Accordingly, theseportions will move as individual laminar panels across the accessopening.

FIGURE 3 illustrates an alternative structure which includes a passageprovided with a honeycomb sec tion 82. The passages in the honeycombsection are shorter in the innermost portions of this section and becomeprogressively longer toward the outer portions of the honeycomb. Withthis arrangement, the air passing through the section will move fasterthrough the inner portions thereof since there will be less drag inthese portions. By providing progressively longer portions, the airpanel passing out of the honeycomb section will comprise a plurality ofindividual sections moving progressively slower in a direction towardthe outside of the cabinet.

The concepts above described are advantageously provided in the passageimmediately adjacent the innermost refrigerated stream. This gradualdecrease in velocity is highly effective in preserving the lowtemperature character of the innermost stream which is in turnresponsible for preserving the temperature of the cold interior portionsof the cabinet. By providing progressively slower portions in the streamadjacent the refrigerated stream, it is possible to virtually eliminateturbulence with respect to outer stream or with respect to the ambientair.

There are many advantages to the system of this invention from thestandpoint of effiiciency of operation. Thus, the provision of thedifferential velocities in the moving streams preserves refrigerationand, at the same time, effects uniformity of temperature within theenclosure. The elimination of a circulating fan for the outer streamdecreases the original cost of the apparatus and provides greatereconomy in its operation. The provision of the third circulating streamalso acts as an additional buffer or barrier, preventing inflow of heat.Finally, the provision of a third circulating stream and its associatedpassage provides for catching of relatively cold air which wouldotherwise spill onto the floor outside the cabinet. By avoiding loss ofthis air, a maximum amount of refrigeration is preserved and, inaddition, discomfort to those standing at the front of the cabinet isavoided. In this latter connection it was observed that an amount ofvery cold air spilled out from the second duct which could be annoyingto one standing in front of the cabinet. By providing a third stream,the air spilled from the second duct is mixed with the warmer air of thethird stream, and, therefore, any air spilling out of the cabinet willbe at a warmer temperature.

it will be understood that various modifications may be made in theabove described construction which provide the features of thisinvention without departing from the spirit thereof, particularly asdefined in the following claims.

That which is claimed is:

1. In a refrigerated cabinet of the type which defines an access openingin one wall communicating an otherwise enclosed space with the ambientatmosphere, and which is provided with a plurality of air inlets and aplurality of air nozzles, said inlets and nozzles extending inside-by-side relationship across opposite edges of said access opening,passages communicating each of the corresponding inlets and nozzles,said passages being independent and being separately defined by the top,bottom and back walls of said cabinet whereby the passages are out ofcommunication with each other and with said enclosed space exceptthrough said inlets and nozzles, and

refrigeration means disposed in at least one of said passages torefrigerate at least the innermost stream passing through said passagesand across said access opening, the improvement comprising means forcirculating the streams of air through said passages and across saidaccess opening in the form of panels, said circulating means beinglocated in each passage except in the passage containing the outermoststream, said outermost stream being circulated through contact of thepanel formed thereby with the moving panel adjacent thereto as thesepanels cross said access opening.

2; A refrigerated cabinet in accordance with claim 1 whereinthree'passages and three circulating streams are provided in saidcabinetand wherein refrigeration means are provided only for the innermoststream, said third stream comprising the outermost stream providing abuffer against the inflow of heat and serving to reduce the amount ofcoldair lost by spilling out of the cabinet and also serving to mix theair spilled from the intermediate passage with warmer air in the thirdpassage thus raising the temperature of the spilled air to a pointnearer ambient temperature.

3. A refrigerated cabinet in accordance with claim 1 wherein saidcirculating means comprise fans located upstream of said refrigerationmeans, and including means for operating the fan in the innermostpassage at a higher rate than the fan in the adjacent passage wherebysaid innermost panel moves at a higher speed than the panel adjacentthereto.

4. In a refrigerated cabinet defining an access opening in one wallcommunicating the otherwise enclosed space with the ambient atmosphere,at least two passages defined in said cabinet each terminating at oneend in an air inlet and at the other end in an air nozzle, said passagesbeing independent and being separately defined by the top, bottom andback walls of said cabinet whereby the passages are out of communicationwith each other and with said enclosed space except through said inletsand nozzles, said inlets and nozzles being disposed in side-by-siderelationship on opposite sides of said access opening, and refrigerationmeans located in at least one of said passages for refrigerating atleast the stream of air passing through the innermost passage, theimprovement comprising circulating mean-s located in the passageconfining said refrigerated stream and in the passage immediatelyadjacent thereto, and means for operating the circulating means in thepassage confining the refrigerated stream at a higher rate than thecirculating means in said adjacent passage whereby the innermost air.panel formed by said refrigerated stream as it crosses said accessopening is adapted to move at a greater speed than the adjacent panel,said circulating means being adapted to maintain the relative rates ofspeed of said panels Within limits permitting slipping between thepanels and avoiding significant turbulence between panels including athird passage located outwardly of the two other passages and having anair inlet and air nozzle at its ends, said third passage confining astream of air which forms an air panel passing in contact with saidadjacent panel, this contact providing for circulation of the stream insaid third passage.

5. In a refrigerated cabinet of the type which defines an access openingin one wall communicating an otherwise enclosed space with the ambientatmosphere, passages comprising an inner passage, an intermediatepassage and an outer passage, each of said passages terminating at oneend in an air inlet and at the other end in an air nozzle, saidpassagesbeing independent andbeing separately defined by the top, bottom andback walls of said cabinet whereby the passages are out of communicationwith each other and with said enclosed space except through said inletsand nozzles, saidinlets and nozzles being disposed in side-by-siderelationship on opposite sides of said access opening, and refrigerationmeans located in at least said inner passage, the improvement comprisingmeans for circulating streams of air through said passages therebyforming three adjacent moving panels of air across said access opening,said circulating means comprising fans in each of said inner andintermediate passages, the fan in saidinner passage being adapted tocirculate the stream in the inner passage at a speed greater than thestream in the intermediate passage, the stream in said outer passagebeing circulated through contact of the outermost panel with theintermediate panel, said circulating means being adapted to maintain therelative rates of speed of said'panels within limits permitting slippingbetween the panels and avoiding significant turbulence between panels.

6. In a refrigerated cabinet defining an access opening in one wallcommunicating the otherwise enclosed space with the outside atmosphere,.at least two passages defined in said cabinet each terminating at oneend in an air inlet and at the other end in an air nozzle, said passagesbeing independent andbeing separately defined by the top, bottom andback Walls of said cabinet whereby the passages are out of communicationwith each other and with said enclosed space except through said inletsand nozzles, said inlets and nozzles being disposed in sideby-siderelationship on opposite sides of said access opening, and refrigerationmeans located in atleast one of said passages for refrigeration of atleast thestreams of air passage throughthe innermost passage, theimprovement comprising means providing for circulation of streams of airthrough said passages thereby. producing adjacent moving panels of airacross said opening, said circulating means including at least one fanlocated in the innermost passage, the streams in a passage adjacent saidinnermost passage being circulated through contact of the adjacent airpanel with the panel corresponding to said innermost stream, saidcirculating means being adapted to maintain the relative rates of speedof said panels within limits permitting slipping between the panels andavoiding significant turbulence between panels.

References Cited by the Examiner UNITED STATES PATENTS WILLIAM J. WYE,Primary Examiner.

ROBERT A. OLEARY, Examiner.

1. IN A REFRIGERATED CABINET OF THE TYPE WHICH DEFINES AN ACCESS OPENINGIN ONE WALL COMMUNICATING AN OTHERWISE ENCLOSED SPACE WITH THE AMBIENTATMOSPHERE, AND WHICH IS PROVIDED WITH A PLURALITY OF AIR INLETS AND APLURALITY OF AIR NOZZLES, SAID INLETS AND NOZZLES EXTENDING INSIDE-BY-SIDE RELATIONSHIP ACROSS OPPOSITE EDGES OF SAID ACCESS OPENING,PASSAGES COMMUNICATING EACH OF THE CORRESPONDING INLETS AND NOZZLES,SAID PASSAGES BEING INDEPENDENT AND BEING SEPARATELY DEFINED BY THE TOP,BOTTOM AND BACK WALLS OF SAID CABINET WHEREBY THE PASSAGES ARE OUT OFCOMMUNICATION WITH EACH OTHER AND WITH SAID ENCLOSED SPACE EXCEPTTHROUGH SAID INLETS AND NOZZLES, AND REFRIGERATION MEANS DISPOSED IN ATLEAST ONE OF SAID PASSAGES TO REFRIGERATE AT LEAST THE INNERMOST STREAMPASSING THROUGH SAID PASSAGES AND ACROSS SAID ACCESS OPENING, THEIMPROVEMENT COMPRISING MEANS FOR CIRCULATING THE STREAMS OF AIR THROUGHSAID PASSAGES AND ACROSS SAID ACCESS OPENING IN THE FORM OF PANELS, SAIDCIRCULATING MEANS BEING LOCATED IN EACH PASSAGE EXCEPT IN THE PASSAGECONTAINING THE OUTERMOST STREAM, SAID OUTERMOST STREAM BEING CIRCULATEDTHROUGH CONTACT OF THE PANEL FORMED THEREBY WITH THE MOVING PANELADJACENT THERETO AS THESE PANELS CROSS SAID ACCESS OPENING.